1. Field of the Invention
The present invention relates to a seal assembly for providing a fluid tight seal between a pipe and an opening in the wall of a structure, such as an underground structure in an underground pipeline system.
2. Description of the Related Art
Seal assemblies are used to provide fluid tight seals between pipes and structures in underground pipeline systems, such as septic tanks and fluid distribution boxes in sewer systems, for example. The structures are commonly made of cast concrete, rigid plastic, fiberglass, or metal, for example, and include a plurality of walls having one or more openings through which pipes extend. The seal assemblies are used to provide fluid tight seals between the wall openings and the outer surfaces of the pipes.
Concrete structures are typically formed with relatively thick walls, and gaskets used with concrete structures include cast-in gaskets and expansion-type gaskets which are made entirely of a resilient material such as rubber. Cast-in gaskets include an annular body having an outwardly-projecting anchor component or flange which is cast within the concrete of the wall such that, when the concrete cures, the flange is embedded within the cured concrete to firmly anchor the gasket within the wall opening. Cast-in gaskets also include either an inwardly-projecting sealing projection or lobe for providing a compressive seal with the outer surface of a pipe, or a resilient boot portion which is sealingly clamped to the outer surface of the pipe with a take-down clamp. Expansion-type gaskets include an annular body which, after being placed within the opening in the structure wall, is radially compressed by an expansion ring assembly to compressively seal the gasket against the wall opening. Thereafter, a take-down clamp is used to sealingly clamp a boot portion of the gasket against the outer surface of a pipe.
Although cast-in and expansion-type gaskets are effective for concrete or other structures having relatively thick walls, these types of gaskets can be less effective or, in some circumstances cannot be used at all, with structures having relatively thin walls which are made of a rigid plastic, fiberglass, or a metal, for example. In particular, the foregoing materials do not easily accommodate cast-in gaskets, and the relatively thin walls of such structures do not provide a sufficiently wide opening surface to which a gasket can be radially compressed using an expansion ring assembly.
One known seal assembly includes an elastomeric body with a rigid, threaded flange, and a nut threadable onto the threads of the flange to compress a portion of the elastomeric body into engagement with an internal wall of a structure about an opening in the structure. Thereafter, after a pipe is extended through the elastomeric body, an external take-down clamp is used to clamp a portion of the elastomeric body around the external surface of the pipe to provide a seal between the gasket body and the pipe.
A disadvantage of the foregoing seal assembly is that same requires the use of an external take-down clamp to provide a seal between the gasket body and a pipe, necessitating additional parts and increasing the number of installation steps. Also, because nearly all of the body of the seal is made of elastomeric material, which tends to be more expensive than other materials, the cost of the seal assembly is relatively high.
Another known seal assembly which is designed for use with relatively thin-walled structures includes a generally cylindrical body made entirely of plastic and including external threads, an annular flange spaced from the threads and projecting radially from the body, and an internal wall which includes a plurality of tear-out portions which may be selectively removed to provide openings of different sizes through the internal wall of the body. In use, the cylindrical body is inserted through an opening in a structure, and a separate annular nut is threaded onto the external threads of the body to capture the wall of the structure between the nut and the annular flange, and the flange is deflected to engage with and seal the side of the wall opposite the nut. Thereafter, one of a plurality of tear-out portions of the internal plastic wall is removed, and a pipe is inserted through the resulting opening in the internal wall, with the plastic wall opening slidably engaging the outer surface of the pipe to provide a deflection or wiper-type seal.
A disadvantage with the foregoing seal assembly is that the deflection or wiper-type seals between the plastic annular flange of the seal body and the wall surface, and between the opening in the internal plastic wall of the body and the outer surface of the pipe, are typically not very robust and may be prone to failure, particularly under fluid pressure. Also, failure of the plastic tear-out portions upon their removal could compromise the integrity of the seal between the seal body and the pipe, particularly when the seal assembly is used with small diameter pipes.
What is needed is a seal assembly for providing a fluid tight seal between a pipe and an opening in a structure, particularly a thin-walled structure made of a rigid plastic or of metal, which is an improvement over the foregoing.